Question

A ray of light strikes a glass slab at $90°$. The angle of incidence is:

• A. $90°$
• B. zero
• C. less than $90°$, but not zero
• D. none of these

Answer 1

The correct option is B

zero

Explanation for the correct option(s):

B: zero

1. When a light ray strikes the glass surface perpendicularly or at a $90°$ angle to the surface, it will pass through without altering direction.
2. The angle of incidence is always zero in this scenario.

Explanation for the incorrect option(s):

A: $90°$

There is no change in direction of the light ray.

C: less than $90°$, but not zero

Due to no change in direction, the angle of incidence cannot have a positive measure.

D: none of these

The angle of incidence, in this case, will be zero.

So, when a ray of light strikes a glass slab at $90°$, the angle of incidence is zero.